The front Mustang II IFS came with disc brakes and the Mustang rear end came with drum brakes. I purchased a 7" master cylinder from Pirate Jacks along with the 2 lb and 10 lb pressure valves and the combination valve as per picture below.
The picture below shows the Chevy 1937-48 pedal assembly 7" dual diaphragm booster, master cylinder, pedal assembly (PBUC3748) bolted on the frame. It uses the same bolt holes as the original master cylinder. The blue residual check valve (RPV2 - 2lbs), red residual valve (RPV10 - 10lbs), and proportioning valve kit (PV2K-1) are shown in the picture.
*Appendum added in 2022*
If I was to do this build again, I would put the brake booster on the firewall. The location on the frame blocks the ability to run the exhaust out the rear of the car!
Because of the size (length) of the new brake assembly, the original access hole to the master cylinder could not be used. The new master cylinder access would line up directly under the driver's seat! I had to purchase a remote master cylinder reservoir in order to add brake fluid without removing the seat!
The picture above shows the Kugel Komponents double reservoir (#5542701) with the red hoses. I had a lot of leaking with the aluminum remote style cover which replaced the cover that came with the master cylinder. I ended up using 2 large hose clamps to hold the cover tight. This stopped the leaking entirely but I am not sure if this solution is legal!
The Emergency Brakes
The picture below shows the old emergency brake cables which I will be replacing.